1. Field of the Invention
This invention relates to fluid jet cutting systems.
2. Prior Art
Within the prior art a number of devices and methods utilizing high velocity fluid cutting jets are known. This prior art may be divided roughly into several general categories. The first category generally concerns itself with experimental techniques directed toward establishing a proof of concept of the high velocity fluid jet technique. As found in Machine Design, on pages 89-93, of Feb. 22, 1973, these techniques generally involve pressurizing a working fluid which is subsequently ejected using a high velocity discharge nozzle. Several relatively early U.S. Pat. Nos. 2,985,050 and 3,212,378, are representative of prior art experimental devices. The lack of commercial success of these devices is generally attributed to the problem of dispersion of the working fluid upon ejection from the nozzle. This has resulted in poor or irregular penetration of cutting along the prescribed path and, additionally, tends to wet the surface. In view of these general problems, prior art fluid jet cutters have been used for cutting rough materials, such as ceramics, metal, lumber and the like.
Additionally, in order to shape or maintain the fluid flow, the prior art demonstrates basic research into the use of additives in the fluid. The use of such additives has been attempted as a means of overcoming the problem of wetting in high velocity systems. U.S. Pat. No. 3,136,649 shows the use of a reinforcing material such as a hardenable resin to support the edges of a cut in a perforating system, and U.S. Pat. No. 3,524,367 utilizes a long chain polymer as an additive to the fluid to increase cohesiveness and minimize dispersion of the fluid upon exiting from the jet. A variation is shown in U.S. Pat. No. 3,532,014 where the cutting rate of the fluid is optimized to volatilize the retained fluid in the edges of the cut by heat due to the frictional engagement of the material with the liquid jet. Such a system, while providing a solution to the problem of wetting, results in materially lower cutting rates and a general inability to cut multiple layers of material.
A second category of prior art centers about attempts to bring this basic research to the point of commercialization with conceptualized systems or components. Typical attempts are shown in U.S. Pat. No. 3,370,040 in which a proposed fluid jet catcher is disclosed. Since the fluid jet, once the cutting area has been traversed, still contains considerable energy, some technique or means must be provided for receiving that jet and effectively dispersing it without the problems of splashback or destruction of the device itself. The Chadwich et al U.S. Pat. No.(3,730,040) is one such prior art attempt at solving the problem of catching the fluid. Similarly, U.S. Pat. No. 3,625,813 discloses the use of a fluid jet cutter for making cuts in paper webs. As previously disclosed, very coarse cuts are made in the loosely matted material, and the jet may be selectively moved across the cutting surface as the material moves past it in an orthogonal direction.
Another attempt at defining a complete system is found in U.S. Pat. No. 3,877,334. This patent builds on basic cutter blade or knife edge technology by utilizing a vacuum chamber underneath the cutting table to position and hold the material. The problem of dispersion of the cutting fluid itself selectively, either by utilizing a honeycombed grid or a generalized porous bed, or as shown in FIG. 4 of that reference, the use of movable belts with the jet constrained to move in one direction and a trough disposed between the belts for receiving the fluid jet once it has exited the cutting surface. In the Gerber U.S. Pat. No.(3,877,334), basic techniques such as X - Y positioning are shown coupled together with the maintenance of a vacuum underneath the cutting table to position the material to be cut. None of these systems has been brought to the point of commercial application.
The third category of prior art deals with systems which have reached the point of commercial implementation and have been used in actual production. U.S. Pat. No. 3,978,784 (assigned to the same company as the present application) defines a commercially successful technique utilizing X - Y positioning controlled by computer and a fluid jet cutter slaved to the movement of the cutting head for movement with the carriage and the cutter, thereby maintaining registration to receive and disperse the fluid which is dispelled once it has passed through the cutting table. The Leslie and Higgins patent utilizes an arm with two segments, shown best in FIG. 5, which contain convoluted steel tubing to form torsional springs at the pivot points. The use of such arms provides a means for bringing high pressure water to the cutting head 44, yet allowing movement of the arms such that it can facilitate traversal of the entire cutting surface 20 by the carriage. This present application builds on the teachings of the Leslie and Higgins invention by providing material improvements in two distinct areas, fluid handling to the cutting heads and increased flexibility in production by using a multiple head arrangement.